Isomerization of cyclic hydrocarbons

ABSTRACT

Saturated cyclic hydrocarbons having a carbon range of from seven to 50 carbon atoms are isomerized by contacting with sulfuric acid having an H2SO4 equivalent in the range of 85 to 102 percent by weight or fluorosulfonic acid and an adamantane hydrocarbon containing zero to four alkyl groups and at least one unsubstituted bridgehead position.

United States Patent Moore 15] 3,6715%8 1451 June 20, 1972 [54]ISOMERIZATION OF CYCLIC HYDROCARBONS [52] US. Cl. ..260/666 M, 260/666P, 260/666 R [51] ..C07c 3/54, C070 13/78 [58] Field of Search ..260/666M, 666 P, 666 R [56] References Cited UNITED STATES PATENTS 3,382,2885/1968 Schneider ..260/666 3,546,308 12/1970 Moore ..260/666 M Primaryliraminer-Delbert E. Gamz Assistant E.\-aminerveronica OKeefeAttorney-Donald R. Johnson, Wilmer E. McCorquodale.

George L. Church, Donald R. Johnson and John F. McNally [57] ABSTRACTSaturated cyclic hydrocarbons having a carbon range of from 1 seven to50 carbon atoms are isomerized by contacting with sulfuric acid havingan H 80 equivalent in the range of 85 to 102 percent by weight orfluorosulfonic acid and an adamantane hydrocarbon containing zero tofour alkyl groups and at least one unsubstituted bridgehead position.

10 Claims, No Drawings ISOMERIZATION OF CYCLIC HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS My copending application Ser.No. 127,784, filed Mar. 24, 1971 of even date herewith discloses andclaims the preparation of conjugated dienes of polycyclic naphthenescontaining three or more fused rings by contacting the polycyclicnaphthenes with a strong acid and an adamantanol compound having atleast one unsubstituted bridgehead position. This reaction may beconducted at a temperature between the freezing point of the acid and 50C.

BACKGROUND OF THE INVENTION 1. Field of the Invention v This inventionrelates to a novel catalytic process for the isomerization of saturatedcyclic hydrocarbons containing from seven to 50 carbon atoms having oneor more saturated rings and containing at least five carbon atoms ineach ring.

2. Description of the Prior Art Various catalytic methods have been usedfrom time to time for the isomerization of hydrocarbons. Many haverequired high temperature operation, expensive or hard to handlecatalysts, expensive corrosion-resistant equipment and/or complexrecovery procedures in order to carry these isomerization reactions. Tobe more specific, the standard catalytic methods for the isomerizationof hydrocarbons use aluminum halides, hydrogen fluoride and the like.

It would be desirable if methods were available which employedrelatively cheap catalyst materials. But even more importantlyeconomically convenient procedures involving simple catalyst systemswhich are easy to handle, enable the isomerization reaction to takeplace at mild conditions and do not involve a complex or difficultseparation and recovery procedure would be highly advantageous. Inaddition it would I be desirable if the isomerization procedure wouldnot require any regeneration or conversion of catalysts or a complexseparation and recovery procedure of the products. Likewise, it wouldalso be desirable if the above could be achieved in relatively simpleand inexpensive equipment.

SUMMARY OF THE INVENTION It has now been found, in accordance with thepresent invention, that the isomerization of saturated cyclichydrocarbons containing form seven to 50 carbon atoms having one or moresaturated rings and containing at least five carbon atoms in each ringis catalyzed by either sulfuric acid having an acid strength of 85 to102% H 80 equivalent by weight or fluorosulfonic acid and an adamantanehydrocarbon having zero to four alkyl groups and at least oneunsubstituted bridgehead position.

The present process thus provides a means of preparing a wide variety ofisomerized hydrocarbons having numerous uses, particularly as tractionfluid compositions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The isomerization of thesaturated cyclic hydrocarbon is effected by contacting a mixture of thesaturated cyclic hydrocarbon and the adamantane compound with eitherfluorosulfonic acid or sulfuric acid having an acid strength in therange of 85- l 02% H SO equivalent by weight. The isomerization may beskeletal (position) or cis-trans.

The alicyclic hydrocarbon of the C to C range having at least one fivemembered ring and having zero to six alkyl substituents containing oneto six carbon atoms each can be isomerized according to this invention.The hydrocarbon feed can also be one or more polycyclicperhydroaromatics with two or more fused rings and three to twelve totalrings inclusive. The alicyclic hydrocarbon can contain no alkylsubstituents or can have one to six alkyl groups inclusive. For example,these substituents can be methyl, ethyl, n-propyl etc., or anycombination of these alkyl groups. However, the alkyl substituentsshould be located at positions other than ring junctions. Gemsubstitution of the alkyl groups on rings is permissible.

Any aromatic hydrocarbon that can be hydrogenated to produceperhydroaromatics as defined herein above can be used in the presentprocess. For example the corresponding aromatic hydrocarbon can bederived from sources such as straight run or cracked petroleum fractionsand coal tar. Such aromatic hydrocarbons can serve as suitable startingmaterial and can be readily converted into perhydroaromatics for use inthe present process by complete hydrogenation utilizing a suitablecatalyst. One suitable catalyst for this purpose is Raney nickel.Appropriate hydrogenation conditions when using this catalyst include atemperature of 20 0-275 C., a hydrogen pressure of 2,000-4,000 p.s.i.g.,a catalyst to hydrocarbon weight ratio of 1:4 to l :20 and a reactiontime of 2-12 hours. Other suitable catalysts that can be used includeplatinum, cobalt molybdate, nickel tungstate or nickel sulfidetungstensulfide, with these hydrogenating components being deposited on alumina.Platinum reforming catalysts available commercially can be used for thispurpose also 5 percent rhodium on carbon. These and other catalystsgenerally are used at the same pressure but at higher temperatures thanRaney nickel such as 300-400 C., in order to effect completehydrogenation of the aromatic hydrocarbon.

Table I gives examples of aromatic hydrocarbons that can be hydrogenatedto produce perhydroaromatics for use in the present process.

2,3-cyclopentanolndane \JVV 6,7-cyclopentanoindane 12 i Fluorene 131,2-cyclopentanonaphthalene 13 2,3-cyclopentanonaphthalene s 13 TableI-Conlinucd Number 01 Carbon Aromatic Atoms Structural formula Phenalene(perinaphthane) 13 m Homotetraphth ene 13 Anthracene 14 Phenanthrene 14Indane-l-spiro cyelohexane 14 Q Tetralln-2-spiro cyclopentane 014 /W1,2-;3,4-d1benzocycloheptatrlenc O15 B-methylanthracene C15 Preferredcyclic hydrocarbons which isomerize according to this process comprisethe cyclic hydrocarbons of the C -C,,, range and particularly thefollowing: 1,2-dimethylcyclopentane, 1,2-dimethylcyclohexane, cisdecalin, perhydrophenanthrene, dicyclohexyl and tetrahydromethyl-'dicyclopentadiene.

The adamantane compound used for the present process As shown, thebridgehead carbon atoms customarily are designated by the numerals l, 3,5 and 7 respectively and these bridgehead positions are all equivalentto each in the nuclear structure.

The preparation of adamantane compounds which are useful as catalyticcomponents according to the present invention can be effected by knownprocedures such as those described for example in the following: U.S.Pats. Nos. 3,128,316; 3,275,600; 3,336,405; 3,382,288; 3,383,424;3,437,701; Spengler et al., Erdoel and KohleErdgas-Petrochemie, 15,702-707 (1962) and Hock et al. Recueil 85, 1,045-1053 (1966).

The most preferred adamantane hydrocarbons useful for this process arehydrocarbons of the C -C range and particularly the following:dimethyladamantanes, trimethyladamantanes, ethyladamantanes,methylethyladamantanes and dimethyladamantanes. Some other specificexamples include: adamantane; l-methyladamantane; 2-methyladamantane;1,2- 1,3- and 1,4-dimethyl-adamantane; land 2-ethyladamantanes;1-ethyl-3-methyladamantane; 1 -ethyl-4-methyladamantane; 1,2,4- 1,2,5-,1,3,4-, 1,3,5- and 1,3,6-trimethyladamantanes;l-ethyl-2,4-dimethyladamantane; l-ethyl-3,5- dimethyladamantane;l-ethyl- 3,6-dimethyladamantane; and l-n propyl -3,5-dimethyladamantane.Also members containing higher alkyl groups are: l-andZ-butyladamantanes; 1- methyl-3-propyladamantane; 1,3-dimethyl-5-butyladamantane; l-ethyl-2-methyl-5-hexyladamantane; l-pentyl-4-methyladamantane; 1,3-diisobutyladamantane; n-hexyladamantanes;n-nonyladamantanes; and the like. The molar ratio of the adamantanecompound to the cyclic hydrocarbon can vary widely in the reactionmixture, for example, from 0.1: 1 to 5:1 but preferably 0.5:1 to 1:1.

ln eflecting the isomerization of the cyclic hydrocarbon with sulfuricacid it is highly important that acid strength .should be in the rangeof -102% H 80 equivalent and more preferably 96-l00% H 80 equivalent byweight. As the sulfuric acid strength approaches the upper limit 102% H80 equivalent by weight competing reactions of isomerization anddehydrogenation may occur in some instances. With higher strengths ofsulfuric acid above 102% H 80 equivalent by weight, the reaction isalmost exclusively a dehydrogenation reaction followed by polymerizationof the dehydrogenated product under these strong conditions, in thiscase the dehydrogenation is an unwanted side reaction. The ratio of acidto the saturated cyclic hydrocarbon compound mixture can also varywidely. Generally, a volume excess of the acid relative to the alkylatedadamantane should be used and a volume ratio thereof in the range of 1:1to 20:1 is typically employed.

Another acid found to be quite useful in the present invention isfluorosulfonic acid (FSO H). However, since the fluorosulfonic acid doesnot have oxidizing potentials as great as sulfuric acid concentrationsof fluorosulfonic acid are not critical. It is generally employed atfull strength.

This reaction can be carried out at any temperature between the freezingpoint of the reaction mixture and 100 C. When concentrations of acid inthe lower part of the concentration range are employed, temperatures of65100 C are required to obtain isomerization. Where the strength of theacid is in the higher portion of the range lower temperatures in therange of 0,l5 C. may be employed. The typical range employed is froml0-40 C. The rate of reaction will depend upon the reaction temperatureselected.

When the saturated cyclic hydrocarbon and adamantane hydrocarbon aremixed with the acid, a two phase system is formed since bothhydrocarbons have a relatively low solubility in the acid. Theadamantane hydrocarbon material is preferentially attacked and appearsto convert to the carboni um ion form. When the adamantane hydrocarbonused is a solid at the reaction temperature employed, e.g., adamantaneor l-methyladarnantane or tetramethyl adamantane it is attacked moreslowly than the liquid alkyladamantanes, such as 2-metliyladamantane,lor 2-methyladamantane, any of the dimethyladamantanes,ethylmethyladamantanes, trimethyladamantanes, or tetramethyladamantanehaving one or more nonbridgehead methyl groups. Also as the molecularweight of the saturated cyclic hydrocarbon is increased, the rate ofreaction tends to decrease and longer mixing times are required toeffect isomerization. In cases when a normally solid adamantanehydrocarbon is used, it is advantageous to add it to the acid in theform of finely divided powder to facilitate solubilization.

The process appears to involve a carbonium ion mechanism in which theadamantanyl carbonium ion abstracts a hydride ion from the cyclichydrocarbon. An intermediate carbonium ion of the cyclic hydrocarbon isgenerated which then isomerizes to its most stable form.

After the reaction has been completed, the acid phase is separated fromthe hydrocarbon phase and the latter is distilled to separate thedesired isomerized cyclichydrocarbon from the adamantane hydrocarbon.

The following examples illustrate the invention and are presentedwithout any intention that the invention be limited thereto.

EXAMPLE 1 Run A (The Invention) To 150 cc sulfuric acid (100% H 80,equivalent by weight) was charged a mixture containing 19.2 gramsperhydrophenanthrene (containing about -20 weight percent of the trans,anti, trans, isomer) and 16.4 grams of 1,3- dimethyladamantane (forconvenience DMA"). The mixture was stirred vigorously with a magneticstirrer to emulsify the hydrocarbon phase and the acid phase. Aliquotportions of about 1 cc of the emulsion were taken periodically shakenwith water and then the hydrocarbon layer was analyzed by gaschromatography to follow the isomerization reaction. After 40 minutesthe hydrocarbon phase was separated, washed with water, dried anddistilled to separate the isomerized product from the hydrocarbonmixture. Ninety-five percent of the DMA was recovered which indicatedthat the DMA serves as a catalyst in the reaction. The DMA recovered wasused in other runs.

The isomerized product obtained in 80 percent yield based on chargedperhydrophenanthrene was analyzed by gas-liquid chromotagraphy, nuclearmagnetic resonance, mass spectroscopy, infra-red, elemental analysis andwas identified as 90 percent trans, anti, trans-perhydrophenanthrene,

Run B (Comparative) By way of comparison the above procedure describedabove was repeated but without addition of DMA. The above isomerizationwas not observed.

EXAMPLE 11 This example shows the isomerization of cis-decalin totrans-decalin. Run A A procedure analogous to that of Example I wasfollowed but a sulfuric acid strength of 96% H 80 equivalent by weightwas employed. Specifically a mixture containing 16.4 grams of DMA and13.6 grams cis decalin were stirred vigorously in 150 cc of sulfuricacid (96% R 80 equivalent by weight) at room temperature. After 3 hoursthe hydrocarbon phase, after washing, drying and distilling contained 5percent cis-decalin and 95 percent trans-decalin. Run B Proceeding as inRun A but anhydrous FSO l-1 was used instead of sulfuric acid. After 3hours the reaction product consisted of 7 percent cis-decalin and 93percent trans-decalin. Run C Proceeding as in Run A but substituting19.8 grams (0.1 mole) of l-ethyl-3,S-dimethyladamantane for the DMA,after 3 hours at room temperature the decalin consisted of 92 percenttrans-decalin and 8 percent cis-decalin.

Run D (Comparative) A control was run in which the cis-decalin wastreated as above in Run A but in the absence of DMA. After 3 hours, thedecalin was composed of 95 percent cis-decalin and 4 percenttrans-decalin.

Runs A, B and C are the invention.

EXAMPLE "I A mixture of 11.2 grams 1,2-dimethylcyclohexane and 16.4grams of DMA is treated as described in the example above yielding anequilibrium mixture of 1,3-dimethylcyclohexane and1,4-dimethylcyclohexane. A control run (DMA omitted) showed that theisomerization occured 10 times faster when DMA was present.

Isomerization products prepared by the present invention have utility ascomponents of traction fluid compositions for use in friction ortractive drive systems. Compositions for this purpose have beendescribed, for example in W. C. I-lamman et a]. U.S. Pat. No. 3,411,369,issued Nov. 19, 1968, and US, Pat. No. 3,440,894 issued Apr. 29, 1969.The first-mentioned patent discloses the use of saturated hydrocarbonshaving two to nine fused rings as components of traction fluids, whilethe latter patent describes for the same purpose the use of saturatedcyclic hydrocarbons having one or more rings each containing six carbonatoms. Compounds prepared by means of the present invention constitutecompounds of the types described in these patents as well as othersaturated cyclic hydrocarbons having analogous utility in tractionfluids.

What is claimed is:

1. A process for the isomerization of saturated cyclic hydrocarbonscontaining from between seven and 50 carbon atoms which comprisescontacting said saturated cyclic hydrocarbon under isomerizingconditions in the presence of a strong acid selected from the groupconsisting of fluorosulfonic and sulfuric acid having a strength of 85to 102% H 80, equivalent by weight and an adamantane hydrocarboncontaining zero to four alkyl groups and at least one unsubstitutedbridgehead position.

2. The process according to claim 1 wherein said saturated cyclichydrocarbon contains from seven to 19 carbon atoms.

3. The process according to claim 1 wherein said adamantane compound isl,3-dimethyladamantane.

4. The process according to claim 1 wherein said adamantane isl-ethyl-3,S-dimethyladamantane. I

5. The process according to claim 1 wherein said strong acid isfluorosulfonic acid.

6. The process according to claim 1 wherein said strong acid is sulfuricacid having a strength of 85-102% H equivalent by weight.

7. The process according to claim 1 wherein said strong acid is sulfuricacid having a strength of 96100% H 80 equivalent by weight.

8. The process according to claim 1 wherein the said saturated cyclichydrocarbon contains eight carbon atoms and said adarnantane hydrocarbonis selected from the group consisting of 1,3-dimethyladamantane andl-ethyl-3,5- dimethylada-mantane.

9. The process according to claim 6 wherein the saturated cyclichydrocarbon contains 12 carbon atoms and the adamantane hydrocarbon is1,3-dimethyladamantane.

10. The process according to claim 6 wherein the saturated cyclichydrocarbon contains 14 carbon atoms and the adamantane hydrocarbon is1,3-dimethyladamantane.

t t: i t a:

2. The process according to claim 1 wherein said saturated cyclichydrocarbon contains from seven to 19 carbon atoms.
 3. The processaccording to claim 1 wherein said adamantane compound is1,3-dimethyladamantane.
 4. The process according to claim 1 wherein saidadamantane is 1-ethyl-3,5-dimethyladamantane.
 5. The process accordingto claim 1 wherein said strong acid is fluorosulfonic acid.
 6. Theprocess according to claim 1 wherein said strong acid is sulfuric acidhaving a strength of 85-102% H2SO4 equivalent by weight.
 7. The processaccording to claim 1 wherein said strong acid is sulfuric acid having astrength of 96-100% H2SO4 equivalent by weight.
 8. The process accordingto claim 1 wherein the said saturated cyclic hydrocarbon contains eightcarbon atoms and said adamantane hydrocarbon is selected from the groupconsisting of 1,3-dimethyladamantane and1-ethyl-3,5-dimethylada-mantane.
 9. The process according to claim 6wherein the saturated cyclic hydrocarbon contains 12 carbon atoms andthe adamantane hydrocarbon is 1,3-dimethyladamantane.
 10. The processaccording to claim 6 wherein the saturated cyclic hydrocarbon contains14 carbon atoms and the adamantane hydrocarbon is1,3-dimethyladamantane.